This invention relates to a hinge device of a rotation member, for example, a lid body having a heavy weight such as on an office machine, especially a duplicator or the like, wherein the moment of rotation varies in accordance with a rotation angle. In such a lid body having a heavy weight such as several kgs, a great force is necessary for opening and closing. As a result, an accident such as catching a workman's finger in the lid body can occur during opening or closing of the lid body due to the inertia of the lid body. There has been a lengthy effort to solve this problem in this field.